If You're Asymptomatic, This COVID Test Could Fail You
The country now looks very different from the first pandemic, although the number of cases is higher than ever. With the pandemic showing no signs of slowing, people are relying on coronavirus tests to see if they can see family and friends or walk into large crowds. And many rely on rapid COVID tests, which are designed to get results in minutes, not days. However, this COVID test may not be as accurate for everyone. In fact, a new study has found that a rapid COVID test may not give correct results if you are asymptomatic. Read on to learn more about the accuracy of rapid tests and the future of the coronavirus. Those 5 people will get the COVID vaccine first, says Dr. Fauci.
In a rapid COVID test, more than two-thirds of positive asymptomatic cases were missed.
A middle aged woman in a yellow shirt smiles while wearing a cloth mask
Researchers at the University of Arizona conducted a study of Quidel's rapid antigen test, the New York Times reported earlier this month. When examining asymptomatic patients or those who did not feel sick, only 32 percent of positive cases reported by a slower, laboratory-based PCR test were accurately recorded.
In the study, researchers tested around 2,500 people from June to August. Of the 1,551 randomly selected people without symptoms, 19 tested positive using PCR tests. However, the rapid test only recorded six of these cases. And to learn more about the spread of COVID, this is when someone is most likely to give you COVID, studies show.
However, the rapid test accurately identified more than 80 percent of positive symptomatic cases.
Male patient wearing face mask feeling chest pain in hospital during coronavirus epidemic. The health workers are in the background.
In contrast to asymptomatic cases, this COVID rapid test was able to detect more than 80 percent of the coronavirus infections reported in the PCR test. Of the 885 people who either experienced COVID-like symptoms or who were exposed to the virus, 305 tested positive using the PCR test. In the rapid test, 251 of them were caught, 18 percent were missing.
"The data for the symptomatic group is decent," said Jennifer Dien Bard, PhD, director of the Laboratory for Clinical Microbiology and Virology at Los Angeles Children's Hospital, who was not involved in the study, told the New York Times. "But getting less than 50 percent in the asymptomatic group? That's worse than flipping a coin." And in order for coronavirus symptoms to be on the lookout, these 4 easy-to-miss symptoms could mean you have COVID, experts say.
This may be because rapid tests are not necessarily intended for asymptomatic patients.
Close up of a young woman having a nasal swab test done by his doctor
According to the New York Times, the US Food and Drug Administration (FDA) only allows Quidel tests to be used on people with symptoms, but the use of rapid tests on asymptomatic people has been "strongly recommended" by the federal government. Even the Centers for Disease Control and Prevention (CDC) are warning the public against using a negative result from a rapid COVID test as the sole source of judgment. According to the CDC, there is still "limited data guiding the use of rapid antigen tests as screening tests on asymptomatic individuals to detect or rule out COVID-19 or to determine whether a previously confirmed case is still infectious". For more information on the limitations of this form of testing, see What the White House Outbreak Taught Us About Rapid COVID Testing.
The researchers also believe these results could mean that asymptomatic patients are not as infectious.
Friends outside with masks around their chins
David Harris, PhD, a stem cell researcher and study author, said the antigen tests may have missed certain asymptomatic patients because they carried too little of the virus to spread to someone else. According to the CDC, "rapid antigen tests" detect the presence of a specific viral antigen, so if they can't detect enough coronavirus material to give a positive result, there may not be enough viral load to infect others.
According to Harris, researchers could not detect the live coronavirus from samples taken from volunteers with C.T. Values over 27. And of the 13 asymptomatic patients who failed the Quidel test, 12 had C.T. Values in the 30s. "If I don't have a live virus, I'm not contagious at all," Harris told the New York Times. For more up-to-date information, subscribe to our daily newsletter.
However, other experts say that there is still not enough research to determine the infectivity of asymptomatic people.
young black woman coughing in her arm outside with people in masks behind her
Omai Garner, PhD, the UCLA healthcare system's assistant director of clinical microbiology who was not involved in the study, told the New York Times that there is no evidence that coronavirus non-growth from a person's sample means that they are not contagious. Other experts noted that the University of Arizona did not track the transmission of coronavirus by the participants, so they cannot draw any conclusions about the spread of the virus.
In any case, people should not rely on rapid antigen tests for negative results. Susan Butler-Wu, PhD, a clinical microbiologist at the University of Southern California who was not involved in the study, told the New York Times that people, especially those with known exposure to the coronavirus, should get more accurate and reliable PCR Testing. And if you're worried about getting sick, this is the easiest way to tell if you've been exposed to COVID.
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